The United States announced all air travelers entering the country will need a negative Covid-19 test before departure, as the country hit a record of nearly 4,500 deaths in a single day.

The policy takes effect on January 26 and expands an existing measure targeting Britain, where the strain known as B117 has been tied to a drastic spike in cases, according to AFP.

“Testing does not eliminate all risk, but when combined with a period of staying at home and everyday precautions like wearing masks and social distancing, it can make travel safer,” said Robert Redfield, director of the US Centers for Disease Control and Prevention.

The United States remains the worst-affected country, with around 380,000 — or a fifth — of the world's almost two million dead, despite accounting for just four per cent of the global population.